The present invention relates to magnetic disc drive systems for storing information. More specifically, the present invention relates to a hydrodynamic bearing assembly which provides support and rotation for a high speed spindle element.
The predominant trend in the disc drive industry for the past several years has been to increase track density in order to achieve increased data storage capacity. One of the difficulties which must be overcome in achieving this goal is the ability to maintain tracking position accuracy as the track density increases.
A major source of tracking position inaccuracy in a computer disc drive system is spindle bearing motion which is commonly referred to as "runout". Conventional spindle bearings include ball bearing assemblies which are prone to numerous mechanical problems, such as large runout, substantial wear, capacious manufacturing requirements, and the like.
A hydrodynamic bearing is an alternative to conventional ball bearing spindle systems. In a hydrodynamic bearing assembly, a lubricating fluid functions as the actual bearing surface between a stationary base and the rotating spindle or hub. The lubricating fluid typically includes either air or liquid. The rotating hub causes the fluid to circulate through the hydrodynamic bearing. When the hub is stationary, the fluid is at rest.
Hydrodynamic bearing assemblies suffer from a number of disadvantages. For example, the parts within a hydrodynamic bearing contact each other generally along a line, whereas the parts within a ball bearing assembly contact each other along a point. During use, the stationary parts may contact the rotating hub causing wear. The wear causes undesirable metal particles to be broken away from the bearing assembly. The inner chamber carrying the fluid is sealed to prevent leakage, however, and the particles are carried in the fluid which contaminates the bearing assembly.
The particles carried in the fluid contact the bearing assembly and create additional wear and particles. Furthermore, the particles carried in the fluid can cause inefficient fluid flow. Inefficient fluid flow creates an inefficient bearing which has a shorter life. An inefficient bearing is also prone to runout which degrades motor performance.